Superhigh dose acid is one thing, but the lack of preparation and a lot of alcohol are likely to make him erratic and outside of himself.
I've seen someone drunk taking not really that much 2C-B and completely losing the plot. Became unintelligible and acting super weird, couldn't remember it the next day.
Locking your friend up may sort of enrage him if he doesn't get that way already... would be good to check that he doesn't hurt himself / become desperate. Even if you had antipsychotics on hand, I don't know if they would do much good what with the alcohol...
I guess when people completely lose the plot you can mostly just babysit them and make sure they don't get into trouble... and if they really become a danger to themselves or others, take measures. If you had a reason to believe he could contain himself without being locked up, that would be better so at least it is not torturing to feel caged... but since you probably can't rely on that and don't want to wait until you'd have to force him in if shit gets out of hand, that would be too late and could get even messier.
Professionals will be able to restrain him better if it is really the last resort, but I'd also realize that he is then likely to resist that much more which will also make him hurt himself.